1. Field of the Invention
The present invention relates to microactuators, optical devices and exposure apparatuses, and device manufacturing methods, and more particularly, to a microactuator that drives a driven body, an optical device equipped with the microactuator and an exposure apparatus equipped with the optical device, and a device manufacturing method using the exposure apparatus.
2. Description of the Background Art
Conventionally, in a lithography process for manufacturing electron devices such as semiconductor devices or liquid crystal display devices, a projection exposure apparatus is used that transfers a pattern formed on a mask (such as a reticle, or a photomask) onto a substrate (such as a glass plate, or a wafer), on which a sensitive agent such as a resist is coated, via a projection optical system.
In recent years, various scanning exposure apparatuses of a so-called maskless type have been proposed, which use a variable shaped mask (which is also called an active mask) instead of a costly mask (a mask which is a fixed pattern master), regardless of size of a device pattern. As a kind of this maskless type scanning exposure apparatus, a scanning exposure apparatus that uses a DMD (Digital Micromirror Device) which is a type of a reflective spatial light modulator serving as a variable shaped mask has been proposed (e.g., refer to Kokai (Japanese Unexamined Patent Application Publication) No. 2004-327660). According to the scanning exposure apparatus that uses the DMD as a variable shaped mask, by changing a pattern generated at a variable shaped mask in synchronization with scanning of a substrate stage and by exposing a substrate held on the substrate stage, a desired pattern can be formed on the substrate without difficulty, and also cost reduction and downsizing of the apparatus are possible.
However, when driving a conventional DMD, a time required for drive and a vibration attenuation time (settling time) which was several times longer than the time required for drive were needed. Therefore, there is a possibility that a drive speed required when performing exposure cannot be achieved, and as a consequence, exposure using the DMD cannot be performed.
Further, in the conventional DMD, for example, as shown in FIG. 9, the state of a micromirror was switched between a state indicated by a reference sign M (a state of being inclined with respect to a base BS) and a state indicated by a reference sign M′ (a state of being inclined with respect to base BS in an opposite direction to the state indicated by reference sign M), and when the micromirror was in the state indicated by reference sign M, the micromirror was regarded as being in a so-called ON state. When an illumination light IL is irradiated on the micromirror in this On state, illumination light IL is reflected off a reflection surface of the micromirror and is incident on a projection optical system PL (i.e. exposure is performed using illumination light IL via the micromirror in the ON state). In the meantime, when the micromirror is in the state indicated by reference sign M′, the micromirror is in a so-called OFF state, and illumination light IL incident on the micromirror in this OFF state is reflected off the micromirror, and then is not incident on projection optical system PL.
However, as shown in FIG. 9, the micromirrors in the ON state are disposed along base BS in a state of being inclined with respect to base BS, and therefore the reflection surfaces of the adjacent micromirrors M are deviated from each other by a distance D in a normal line direction of the reflection surfaces of micromirrors M. Accordingly, illumination lights IL via the respective micromirrors M have the phase difference from one another, and such phase difference could affect the exposure accuracy.
Furthermore, an active mask that uses a DMD having a function similar to a phase shift mask is expected to appear in the future.